1. Field of the Invention
This invention relates to a gray scale sync video format that uses the frequency spectrum in FM systems more effectively by replacing the NTSC (National Television System Committee) blacker-than-black sync pulse (which accounts for about 30 percent of the composite signal peak-to-peak deviation) with gray scale sync that permits the picture signal to be increased by an amount equivalent to the 30 percent.
2. Description of the Prior Art
The past several years have witnessed a major increase in utilization of domestic satellites for video distribution systems. This trend is expected to continue at an accelerated pace. In its wake is a strong demand for smaller, lower cost TVRO (Receive Only) stations which are capable of providing NTC-7 (specifications of the Network Transmission Committee of the Video Transmission Engineering Advisory Committee of the Joint Committee of Television Network Broadcasters and the Bell System picture quality performance).
To the best of applicants' knowledge, no one has devised a video gray scale sync processing system whereby the standard video sync pulse and color burst is deleted and subsequently regenerated, no one has ever replaced the color burst and sync signals with pulses containing color reference, audio and horizontal sync information, no one has achieved a 3 dB improvement in picture signal-to-noise ratio (relative to NTSC format), and no one has used the technique of flipping the video scan lines to provide security and symmetrical video spectrum distribution in FM systems.
With respect to the unique audio multiplexing concept of this invention, one current method of transmitting the audio requires a separate carrier which is most wasteful of the satellite spectrum.
A second technique is to introduce the sound at the upper portion of the video bandwidth, resulting in picture information degradation. This requires a low-pass filter which cuts off at 5 mHz. The audio modulates a subcarrier such as 6.2 mHz above the picture information. The disadvantage of this technique of adding audio subcarriers is getting picture information into sound and sound into picture. Also because there is a wider bandwidth, one may get more noise.